1. Field of the Invention
The present invention relates to an improved controlled release carrier system that can be incorporated into soap bars that enhances deposition of active ingredients as well as fragrances onto skin and which prolongs the release of active ingredients and fragrances from the skin over an extended period of time.
2. Description of the Related Art
Consumer acceptance of soap bars is determined not only by the performance achieved with these products but the aesthetics associated therewith. Fragrance is an important aspect of the successful soap bars and they are being utilized, in addition to imparting an aesthetically pleasing odor, to convey to the consumer the product performance and effectiveness (i.e., the skin is clean, etc.). Recently, soap bars are utilized not only to clean and disinfect the skin, but also to impart long lasting malodor coverage and the performance features expected from these products are similar to those of deodorants.
Fragrances are typically added to soap bars to provide a fresh, clean impression for these products as well as the skin treated with these products. While the fragrance does not add to the performance of soap bars, it does make these products more aesthetically pleasing and the consumer has come to expect such products to have a pleasing odor. The fragrance plays a major, and often determining, role for the consumer in selecting and purchasing the soap bars. Consumers are becoming increasingly educated and expect a high level of sophistication in their soaps. Many consumers would prefer for the fragrance or the disinfecting actives, present in these products, to be deposited on the skin and remain there for an extended period of time to convey a lasting impression of freshness. Fragrance creation for soaps is restricted not only by considerations such as availability and cost, but also by compatibility of the fragrance ingredients with other components in the product composition and the ability of the fragrance ingredients to deposit onto the skin and survive the rinse process. Furthermore, large amount of fragrance is being lost during washing. Practice has shown that when currently available products are used, a large fraction of the fragrance is lost during the rinse process due to the solubility of certain fragrance ingredients in aqueous washing compositions, and the fraction of the fragrance which was deposited, quickly evaporates, due to the volatility of fragrance ingredients.
Water soluble polymers have also been used to encapsulate fragrance oils. Such capsules have proved useful in releasing perfume in deodorants. However, such capsules have not been commercially successful in extended release of perfume from skin. U.S. Pat. Nos. 5,770,556 and 5,955,409 disclose a process for making bar compositions having enhanced deposition of benefit agent. The patents relate to a process in which specific powder adjuvants comprising (a) benefit agents, (b) a carrier (e.g., soluble or partially soluble starches, water soluble amorphous solids or semi-crystalline water soluble solids), (c) water and (d) optional deposition/processing aids are first prepared and then mixed with bar chips prior to milling, extruding and stamping the bars. The carrier component disclosed by U.S. Pat. No. 5,770,556 is any water soluble starch including both partially soluble starches (such as corn or potato starch) and, more preferably, xe2x80x9ctruexe2x80x9d water soluble starches, i.e., starches in which at least 10% by wt. or greater solution of starch in water will dissolve to form a clear or substantially clear solution. Examples of such include maltodextrin. The carrier may also be a semi-crystalline water soluble solid such as, for example, gelatin. The carrier compound generally will comprise about 15% to 98%, preferably 30% to 50% of the powder composition. These carrier materials will quickly dissolve in water (especially maltodextrins) to release the active and have little chance to enhance deposition of active ingredients onto the skin and sustain their release rate on the skin.
U.S. Pat. No. 5,876,755 discloses a water-sensitive matrix material which can be starch, modified starch, maltodextrin, cyclodextrin, gums, resins, synthetic or semisynthetic polymers such as polyvinyl pyrrolidine (PVP), polyvinylalcohol (PVA) and cellulose esters, and combinations of these materials. The preferred matrix material comprises modified starch. The encapsulating material (i.e. the encapsulated substance within the water-sensitive matrix) is conveniently prepared by spray drying, and is typically particulate so that the composition as a whole is particulate in nature.
U.S. Pat. Nos. 4,803,195 and 5,508,259 also disclose a water soluble encapsulation system that can be incorporated in soap bars. The matrix material utilized in the above patents comprises:
a. a solid film-forming substrate chosen from polyvinyl acetate, polyvinyl alcohol, dextrins, natural or modified starch, vegetable gums, pectins, xanthans, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose and lipoheteropolysaccharides, and
b. an emulsifying agent chosen from mono- or diglycerides of fatty acids, esters derived from the combination of fatty acids with sorbitol or a saccharide, or their alkoxylated derivatives, or an ester of tartaric, citric, ascorbic or lactic acid.
Again, these carrier materials will quickly dissolve in water (especially maltodextrins) to release the active and have little chance to enhance deposition of active ingredients onto the skin and sustain their release rate on the skin.
U.S. Pat. No. 4,749,501 discloses a solid soap composition comprising a soap base and microcapsules dispersed therein, said microcapsules are prepared by using a hydrophobic liquid as a core material, forming microcapsules by covering the hydrophobic liquid with coacervate of a hydrophilic material, and then adding an electrolyte to a solution having the microcapsules dispersed therein in an amount of 8 to 100 parts by weight to 100 parts by weight of the water used in the microcapsules to dehydrate the microcapsule films. The hydrophilic coacervate is an anionic hydrophilic high molecular weight substance is gum arabic, alkali metal salt of carboxymethyl cellulose, sodium alginate, carrageenan, styrene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, acrylic acid copolymer, polyvinylbenzene sulfonic acid, carboxymethyl starch or mixtures thereof. The microcapsules hardly disintegrate during the soap production process but do disintegrate during the use of the soap composition when contacted with water. This type of controlled release system has the limitation of not working with all type of fragrance ingredients, especially not with fragrance ingredients that are relatively water-soluble and do not deposit into the skin.
A similar system is described in U.S. Pat. No. 6,248,703 which discloses bar compositions comprising a non-water soluble benefit agent core surrounded by a friable coating comprising the reaction product of (1) an amine selected from urea and melamine; and (2) an aldehyde selected from formaldehyde, acetaldehyde and glutaraldehyde; and mixtures of the amines and the aldehydes; wherein the capsules are strong enough to survive a soap extrusion process but sufficiently friable to break upon use of the bar by the consumer.
Perfumes have been adsorbed onto various materials such as silica and cyclodextrins to deliver perfume in soap bars. U.S. Pat. No. 5,723,420 discloses a personal cleansing bar compositions which contains a fragrance-releasing complex and a bar carrier. The fragrance-releasing complex contains a hydrophilic inorganic porous fragrance carrier and a fragrance impregnated within the fragrance carrier. Inorganic carriers include amorphous silica, precipitated silica, fumed silica and aluminosilicates such as zeolite and alumina. Another type of inorganic carrier suitable for use in the present invention include cyclodextrin. This system has the drawback that the fragrance oil is not sufficiently protected and is frequently lost or destabilized during processing.
Attempts to enhance deposition of fragrance onto skin have been described in U.S. Pat. No. 5,476,660 which discloses compositions to deposit an active substance on a target surface. The active substance is left on the surface after the product is rinsed off the surface. The preferred deposition is from compositions containing an anionic or nonionic active in the co-presence of an anionic surfactant. The compositions contain carrier particles having a zwitterionic or cationic surface and a plurality of outwardly protruding filaments containing charged organocarbyl groups. The term xe2x80x9czwitterionicxe2x80x9d as described in this patent means a mixture of cationic and anionic (not necessarily neutral); thus the surface of the zwitterionic particles, have both cationic and anionic groups (i.e., positively charged and negatively charged organocarbyl groups). The filaments are formed from an emulsion comprising molten wax, an anionic surfactant and a cationic surfactant. The active substance is contained within the carrier particles.
The major challenge in designing controlled delivery systems for soap bars is maximizing the deposition of the system comprising the active ingredients onto the skin. There remains a need in the art for an efficient controlled delivery system, to effectively deposit active ingredients, as well as fragrances, onto skin and for a method to xe2x80x9cboostxe2x80x9d the overall charge density of particles thereby providing enhanced deposition onto the skin.
The prior art of which applicant is aware does not set forth a fragrance controlled release system that can be incorporated in a soap bar to enhance deposition of active ingredients, as well as fragrances, especially not for fragrance ingredients that are more soluble into the aqueous phase of the washing compositions and do not deposit onto the skin. There is also a need for a fragrance carrier system, for soap bars, that will allow using a wider range of fragrance ingredients that are currently not substantive on skin from a soap bar application and improved fragrance substantivity and longevity onto the skin. It is desirable to provide a control release system for overcoming these limitations. It is also desirable to provide a method using an efficient and economical process for effectively delivering a broad range of fragrances and other ingredients onto skin and yields a high impact fragrance xe2x80x9cburstxe2x80x9d upon washing and a prolonged fragrance release from the skin over an extended period of time.
The present invention relates to an improved controlled delivery system for active ingredients and sensory markers from soap bars, to enhance deposition of the active ingredients and sensory markers onto the skin and extend their release rate over a prolonged period of time. The controlled delivery system of the present invention is a multi-component system comprising of positively charged solid hydrophobic nanospheres encapsulated in a moisture sensitive microsphere. Active ingredients, as well as sensory markers such as fragrances, can be incorporated in the nanosphere matrix, in the microsphere matrix, or in both the nano and microsphere matrices. The nanosphere surface has high cationic charge density to improve the deposition of the nanospheres onto the skin. The high cationic charge density on the nanosphere surface is created by incorporating a cationic conditioning agent into the solid hydrophobic matrix of the nanospheres, by incorporating a cationic charge xe2x80x9cboosterxe2x80x9d in the water sensitive microsphere matrix, or by using a cationic conditioning agent in the nanosphere matrix in conjunction with a cationic charge xe2x80x9cboosterxe2x80x9d in the microsphere to matrix. The delivery system of the present invention also yields a high impact fragrance xe2x80x9cburstxe2x80x9d upon wash with the system and provides controlled release or prolonged fragrance release from the treated skin over an extended period of time.
In one embodiment, the present invention provides an improved fragrance carrier system for soap bars which has improved fragrance substantivity to bring the fragrance onto skin that has been washed with the soap bar comprising the fragrance carrier system. In the fragrance industry, the term xe2x80x9csubstantivityxe2x80x9d refers to the deposition of the fragrance on the skin and the retention and perception of the fragrance on skin treated with the soap bar. The fragrance carrier system of the present invention provides cationic surface-active agents to allow a wide range of fragrances and fragrance ingredients to be compatible within the carrier composition and increase the substantivity of fragrances and fragrance ingredients that are currently not substantive on skin after wash with conventional soap bars. The fragrance-carrier system yields a high impact fragrance xe2x80x9cburstxe2x80x9d upon wash and provides prolonged fragrance release over an extended period of time. In addition, the production of the carrier system utilizes minimum processing steps and is efficient and economical.
The carrier system of the present invention is a free-flowing, powder formed of solid hydrophobic positively charged nanospheres comprising various active ingredients, as well as fragrances, that are encapsulated in a moisture sensitive microspheres, characterized by:
(i) protection of the active ingredients, as well as the volatile constituents of the fragrance, during storage, until needed;
(ii) yield high impact fragrance xe2x80x9cburstxe2x80x9d upon wash;
(iii) moisture triggered release of the nanospheres comprising the active ingredients, as well as the fragrance, in response to moisture (upon wash),
(iv) enhanced deposition of active ingredients and fragrances onto skin; and
(v) prolonged release of active ingredients and fragrances from the skin over an extended period of time.
The invention also provides a method for producing a multi component controlled release system of the present invention including active ingredients and a fragrance that comprises the steps of:
(i) incorporating a cationic conditioning agent, active ingredients, and fragrance into the solid hydrophobic nanospheres;
(ii) forming an aqueous mixture comprising of one or more active agents, a fragrance, the nanospheres, a cationic charge booster, and a moisture sensitive material, such as, starch derivatives, natural gums, polyvinyl alcohol, proteins, hydrocolloids, or mixture of thereof; and
(iii) spray drying the mixture to form a dry powder composition.
The invention further provides a process for producing the multi component controlled release system of the present invention that comprises the steps of:
(i) heating hydrophobic materials to a temperature above the melting point of the materials to form a melt;
(ii) dissolving or dispersing a cationic conditioning agent into the melt;
(iii) dissolving or dispersing a first fragrance and a first active agent into the melt;
(iv) dissolving or dispersing a second active agent, a second fragrance, a cationic charge booster, and moisture sensitive material, such as, starch derivatives, natural gums, polyvinyl alcohol, proteins, hydrocolloids, or mixture of thereof, in the aqueous phase;
(v) heating the composition to above the melting temperature of the hydrophobic material;
(vi) mixing the hot melt with the aqueous phase to form a dispersion;
(vii) high shear homogenization of the dispersion at a temperature above the melting temperature until a homogeneous fine dispersion is obtained having a sphere size of from about 1 micron to about 2 microns;
(viii) cooling the dispersion to ambient temperature; and
(ix) spray drying the emulsified mixed suspension to form a dry powder composition.
The incorporation of spray dried nanospheres comprising fragrances and other active agents encapsulated within a moisture sensitive matrix in soap bars was found to enhance fragrance deposition onto skin, and to extend the release rate of these fragrances and active ingredients over an extended period of time. In an alternate embodiment, a controlled release composition is formed of hydrophobic nanospheres incorporating active agents. It has been found that a key to maximizing deposition of the system onto the skin is optimized particle size of the nanospheres of the present invention to ensure that the particles stay on the skin and have a sufficiently high cationic charge density on the particle surface to maximize ionic interaction between the particles and the skin.
It is believed that the cationic charge groups on the nanospheres surface become associated, in use of the composition, with the skin and assist in adhering the nanospheres onto skin during the wash through both sphere entrainment and electrostatic interactions to effectively deliver fragrance onto skin and sustain fragrance release rate. The hydrophobic matrix sustains the diffusion rate of the fragrance through the nanospheres and enables the fragrance to be released from the skin over an extended period of time.
The invention also provides soap bars comprising the multi component controlled release system of the present invention. Skin treated with a soap bar comprising the multi component controlled release system of the present invention was observed to exhibit a high level of fragrance (high odor intensity) and fragrance perception on skin (the level of fragrance and fragrance perception on skin) has been observed to perceived over an extended period of time, such as about 48 hours.
The present invention addresses the foregoing need to increase the deposition of wide range of fragrances and active ingredients onto skin and prolong their release so that the skin remains aesthetically pleasing for an extended period of time by employing an advanced carrier system to deposit the fragrance and other active ingredients onto the skin.
The carrier system of the present invention can be incorporated into any soap bar product and soap compositions and provide long-term storage stability.